This invention relates generally to holography and more specifically to high density storage of color visual information on a monochromatic photosensitive record member.
The invention of off-axis holography is described by Leith and Upatnieks in the Scientific American, June, 1965, pages 25-35, and in their copending patent application Ser. No. 361,977. Briefly described, the basic off-axis holographic technique includes interfering two coherent beams of light, which are also coherent with each other, at a photosensitive detector and at some finite angle with each other. One of the beams contains in its wavefront the information to be recorded. For instance, one of the beams may be modified by an object. The other beam serves as reference energy and thus, the phase and amplitude of the information carrying wavefront are recorded on the hologram detector. The information carrying wavefront is reconstructed from the finished hologram upon its illumination with coherent light in a beam that is physically related to the reference wavefront beam used to construct the hologram. A viewer positioned in the path of this reconstructed information carrying wavefront is able to observe an image of the original object in full three-dimensions as if he were observing the object itself.
There are various modifications of this basic off-axis holographic technique that provide for reconstructing three-dimensional images in full color. One example of a color holographic technique is described in the aforementioned article and copending patent application, wherein an object is holographically recorded on one monochromatic photosensitive detector by constructing a distinct hologram for each of three primary colors. Each of these distinct holograms is readout by coherent light of a different wavelength, thereby to reconstruct three monochromatic images of an object which are superimposed to form a full color image of an object. A disadvantage of such techniques is the necessity for use of coherent light containing three different colors since either three individual laser sources or a complicated three color laser is required.
Therefore, it is an object of this invention to provide a color holographic recording technique wherein full color information may be retrieved with a monochromatic light source.
It is also an object of this invention to provide a color holographic recording and playback technique for greatly reducing the area of a record necessary to store a given amount two-dimensional information.
It is a further object of this invention to provide a holographic information storage record containing a large number of independent items of two dimensional color information.
It is an additional object of this invention to provide a technique of holographically recording an ordinary color photographic movie onto a hologram record and to provide a technique of reconstructing an apparently moving picture image from a hologram record for display on a television screen.
It is an object of this invention to provide a simple and reliable television color image converting apparatus.